In the U.S. Pat. application Ser. No. 5,699 filed Jan. 23, 1979 in the name of Robert W. Luebke and entitled Containment Reservoir and Method, there is disclosed a reservoir arrangement formed with a flexible liner laid in an earthen containment space for catching petroleum based liquids discharged from railroad vehicles, such as diesel locomotives, on a railroad track section. The present invention provides an improvement over the arrangement and method disclosed in Ser. No. 5,699.